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Titolo:
IR study of polycrystalline ceria properties in oxidised and reduced states
Autore:
Binet, C; Daturi, M; Lavalley, JC;
Indirizzi:
Univ0Caen, ISMRA, URA CNRS 414, UMR 6506,Lab Catalyse & Spectrochim, F-1405 Univ Caen Caen France F-14050 MR 6506,Lab Catalyse & Spectrochim, F-1405
Titolo Testata:
CATALYSIS TODAY
fascicolo: 2, volume: 50, anno: 1999,
pagine: 207 - 225
SICI:
0920-5861(19990429)50:2<207:ISOPCP>2.0.ZU;2-J
Fonte:
ISI
Lingua:
ENG
Soggetto:
TRANSFORM INFRARED-SPECTROSCOPY; CARBON-MONOXIDE ADSORPTION; ADSORBED PROBE MOLECULES; FAST ACQUISITION MODE; METAL-OXIDE SURFACES; ROOM-TEMPERATURE; PD/CEO2 CATALYSTS; OXYGEN-ADSORPTION; REDOX PROCESSES; PURE CERIA;
Keywords:
ceria; IR study; FT-IR spectroscopy;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
68
Recensione:
Indirizzi per estratti:
Indirizzo: Lavalley, JC Univ Caen, ISMRA, URA CNRS 414, UMR 6506,Lab Catalyse & Spectrochim, 6 Blvd Univ Caen 6 Blvd Marechal Juin Caen France F-14050 m, 6 Blvd
Citazione:
C. Binet et al., "IR study of polycrystalline ceria properties in oxidised and reduced states", CATAL TODAY, 50(2), 1999, pp. 207-225

Abstract

Surface properties of high surface area ceria samples, either in the reduced or unreduced state, have been investigated using FT-IR spectroscopy. Upon reduction, detailed features in the background spectrum of unreduced samples, which may be assigned to surface or multiphonon modes, vanish while weak bands due to electronic transitions appear. One of these bands is assignable to Ce3+ as point defect in the core. Adsorption of probe molecules is used to characterise the Lewis acid-base strength of surface sites. Adsorption of a proton donor (pyrrole) or an electronic acceptor (CO2) is indicative of the high basicity of surface O2- ions for ceria either reduced or not. The acid strength of cerium ions is weak; its decrease upon reduction maybe shown by adsorbing weak Lewis bases (CO, acetonitrile) but not by stronger ones (pyridine, dimethylether). Superoxide (O-2(-)) or peroxide (O-2(2-)) surface species are produced when O-2 is adsorbed on surface reduced defects. In the case of samples with a higher degree of reduction, the electron donor power is shown by tetracyanoethylene adsorption. Surface hydroxy and methoxy species from H-2 and methanol dissociations, respectively, are very sensitive probes in differentiating one, two and threefold co-ordinatively unsaturated cationic sites and their reduction state. The use of methoxyspecies allows to quantify the ceria reduction degree through the additionof known amounts of oxygen. Adsorbed formate species are also sensitive toceria reduction state. (C) 1999 Elsevier Science B.V. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 13/07/20 alle ore 19:15:40